PET is a molecular imaging modality that utilizes trace amounts of radiolabeled molecules (probes) to target, measure, and image biological processes in tissue concentrations down to the range of nano-to picomoles. Imaging technologies from SOFIE and other companies allow the same probes to be used in cell cultures, mice, and patients to integrate findings from each of these settings with other basic science and clinical results. UCLA investigators developed, and licensed to SOFIE for further commercialization, a family of nucleoside analog probes, [18F]FAC, that are transported and trapped intracellularly by dCK phosphorylation. SOFIE and others can now reference UCLA INDs for these probes, allowing further investigation into [18F]FAC as diagnostic agents for assaying dCK enzyme activity in predicting tumor responses to dCK-dependent prodrugs. The main roadblock to widespread use of this probe is that currently, no commercial radiosynthesizer exists for synthesizing [18F]FAC for preclinical and clinical investigations. This proposal will develop a commercial, cGMP-compliant, automated radiosynthesizer and post-processing module to produce [18F]FAC.